How are such things measured?
- Did I "fully" change? (who can say?)
- Could I have changed more? (sure)
- Did I change enough? (who can say?)
Or...
- Did I pursue the love of God on a regular basis? (who can say?)
- Could I have pursued the love of God more? (sure)
- Did I pursue the love of God enough? (who can say?)
Excellent questions--I've certainly asked these question of myself! And I don't know if there will be any completely-satisfactory answers. Ultimately, God is the Judge as to who is presently "Saved" and who is not. Some may not even believe one can truly claim to be "Saved" in the present life--it will be determined in the next life.
I happen to believe we can know we're Saved, whether or not we can become "Unsaved." I don't believe we can become Unsaved, but that remains to be proven, one way or the other. I do believe, based on my own system, that Nominal Christians can become "Unsaved," so to speak, although I don't believe they were ever really "Saved" to begin with.
I truly hate to discuss this subject because a close brother is borderline hostile with me when I discuss it--he's very "Arminian." At any rate, I tend to be a "blunt person," not wishing to avoid any topic whatsoever.
The importance of showing we have a "changed nature" is not just in the volume of good works we do, or in the number of times we "show God's love." Rather, it is in whether the love of God has penetrated our own heart so deeply that we have sacrificed our independence for dependence upon God in order to truly have it.
Anybody can show the love of God. But only the completely committed can "have it." They in effect become "good people," just as God is good. They are no longer carnal people, but participate in the goodness of God. They do not merely "copy Christ." More, they "receive Christ" and "put on Christ."
Granted, someone who "copies Christ" can look very much like they have "received Christ" and "put on Christ." But one can know if they have truly "changed natures" if they "become pure in spirit" and appear to be truly "good people." They truly *are* good people.
But some here have been concerned about my theology on Salvation by Grace. Let me just say this. People aren't saved because they are good people. On the contrary, in choosing to receive Christ they have received Salvation, and so become good people. They have chosen to change natures, and not just do occasional good things from Christianity. They adopt Christ on a permanent basis in order to become good people.
So I would say that the real determining factor in whether someone has truly been Saved is whether they've truly sacrificed having their own way in life for dependence upon the will of God, as revealed in Christ. Do they love to talk about Christ? Do they find it desirable to sacrifice their own carnal ways?
I admit this isn't something that can be easily proven one way or the other. God is the Judge over matters of Salvation. And unless we have it revealed to us, we cannot proclaim one either fully Saved or completely lost, a "child of the Devil."